Promote Tautulli to the primary watch-history source

Tautulli is running at 192.168.1.100:8181, so watch data now comes from
get_history rather than Plex's session history. This matters beyond
convenience: Plex records that a play started, Tautulli records how far it
got. A film three people abandoned after five minutes and a film nobody ever
opened are opposite signals for a deletion decision, and Plex reports them
identically.

- Adds sections 4.8-4.11: Tautulli ingest, completion semantics, fallback,
  coverage horizon, and the pms_identifier cross-check
- Splits MediaProvider into MediaProvider + HistoryProvider so library data
  and watch data can come from different servers
- watch_event gains percent_complete, disposition, source, and session
  merging; media_item gains partial/abandoned counts and pre_history
- New 'rejection' score component, with weights renormalizing when a
  component is unavailable rather than silently scoring everything lower
- Deployment: image built off-box and pushed to Nox's Portainer, versioned
  tags rather than :latest
- Closes three open questions, opens two smaller ones

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GVbG48GAXfCZatcmX123Ra

README.md

@@ -3,11 +3,12 @@
 A self-hosted web app for figuring out which of the thousands of files in a Plex library
 are actually worth keeping.
 
-MediaShelf scans a Plex Media Server over its HTTP API, builds a local snapshot of every
-movie and TV season, and joins together the facts Plex already knows but never shows side
-by side — date added, size on disk, file path, owning library, watch count, and last
-watched — into a sortable, filterable, chartable grid with a tunable **reclaim score**
-that ranks deletion candidates.
+MediaShelf scans a Plex Media Server over its HTTP API and pulls watch history from
+Tautulli, builds a local snapshot of every movie and TV season, and joins together facts
+that are never shown side by side — date added, size on disk, file path, owning library,
+watch count, last watched, and *how much of it anyone actually finished* — into a
+sortable, filterable, chartable grid with a tunable **reclaim score** that ranks deletion
+candidates.
 
 ## Status
 
@@ -22,13 +23,16 @@ Nothing is implemented yet — this repository currently holds the design.
 
 - Full-library ingest from Plex, no agent on the Plex host, no filesystem mounts
 - Movies at item level, TV rolled up to **season** level
-- Watch data pulled from the server-wide playback history, so plays by *every* Plex
-  account are counted — not just the token owner's
+- Watch data from **Tautulli**, so plays by *every* account are counted and a play that
+  was abandoned after five minutes is distinguished from one that was finished — Plex's
+  own history reports those identically. Falls back to Plex session history if Tautulli
+  is unavailable, and says so rather than degrading silently
 - Sort and filter on every metric; charts for size by library, additions over time,
-  watched vs. unwatched by size, and size vs. last-watched
+  finished vs. abandoned vs. never-opened by size, and size vs. last-watched
 - A weighted reclaim score with live sliders, and grace rules so it never recommends
   something you added last week
-- Named, re-runnable saved views — *"unwatched, older than 2 years, over 10 GB"*
+- Named, re-runnable saved views — *"unwatched, older than 2 years, over 10 GB"*,
+  *"two people started it and nobody finished it"*
 - CSV export of any view
 
 ## Planned stack